/*

 * dirhash.c -- Calculate the hash of a directory entry

 *

 * Copyright (c) 2001  Daniel Phillips

 *

 * Copyright (c) 2002 Theodore Ts'o.

 *

 * %Begin-Header%

 * This file may be redistributed under the terms of the GNU Library

 * General Public License, version 2.

 * %End-Header%

 */

#include "config.h"

#include <stdio.h>

#include <string.h>

#include <limits.h>

#include "ext2_fs.h"

#include "ext2fs.h"

#include "ext2fsP.h"

#ifndef PATH_MAX

#define PATH_MAX 4096

#endif

/*

 * Keyed 32-bit hash function using TEA in a Davis-Meyer function

 *   H0 = Key

 *   Hi = E Mi(Hi-1) + Hi-1

 *

 * (see Applied Cryptography, 2nd edition, p448).

 *

 * Jeremy Fitzhardinge <jeremy@zip.com.au> 1998

 *

 * This code is made available under the terms of the GPL

 */

#define DELTA 0x9E3779B9

static void TEA_transform(__u32 buf[4], __u32 const in[])

{

  __u32 sum = 0;

  __u32 b0 = buf[0], b1 = buf[1];

  __u32 a = in[0], b = in[1], c = in[2], d = in[3];

  int n = 16;

  do {

    sum += DELTA;

    b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);

    b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);

  } while(--n);

  buf[0] += b0;

  buf[1] += b1;

}

/* F, G and H are basic MD4 functions: selection, majority, parity */

#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))

#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))

#define H(x, y, z) ((x) ^ (y) ^ (z))

/*

 * The generic round function.  The application is so specific that

 * we don't bother protecting all the arguments with parens, as is generally

 * good macro practice, in favor of extra legibility.

 * Rotation is separate from addition to prevent recomputation

 */

#define ROUND(f, a, b, c, d, x, s)  \

  (a += f(b, c, d) + x, a = (a << s) | (a >> (32-s)))

#define K1 0

#define K2 013240474631UL

#define K3 015666365641UL

/*

 * Basic cut-down MD4 transform.  Returns only 32 bits of result.

 */

static void halfMD4Transform (__u32 buf[4], __u32 const in[])

{

  __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

  /* Round 1 */

  ROUND(F, a, b, c, d, in[0] + K1,  3);

  ROUND(F, d, a, b, c, in[1] + K1,  7);

  ROUND(F, c, d, a, b, in[2] + K1, 11);

  ROUND(F, b, c, d, a, in[3] + K1, 19);

  ROUND(F, a, b, c, d, in[4] + K1,  3);

  ROUND(F, d, a, b, c, in[5] + K1,  7);

  ROUND(F, c, d, a, b, in[6] + K1, 11);

  ROUND(F, b, c, d, a, in[7] + K1, 19);

  /* Round 2 */

  ROUND(G, a, b, c, d, in[1] + K2,  3);

  ROUND(G, d, a, b, c, in[3] + K2,  5);

  ROUND(G, c, d, a, b, in[5] + K2,  9);

  ROUND(G, b, c, d, a, in[7] + K2, 13);

  ROUND(G, a, b, c, d, in[0] + K2,  3);

  ROUND(G, d, a, b, c, in[2] + K2,  5);

  ROUND(G, c, d, a, b, in[4] + K2,  9);

  ROUND(G, b, c, d, a, in[6] + K2, 13);

  /* Round 3 */

  ROUND(H, a, b, c, d, in[3] + K3,  3);

  ROUND(H, d, a, b, c, in[7] + K3,  9);

  ROUND(H, c, d, a, b, in[2] + K3, 11);

  ROUND(H, b, c, d, a, in[6] + K3, 15);

  ROUND(H, a, b, c, d, in[1] + K3,  3);

  ROUND(H, d, a, b, c, in[5] + K3,  9);

  ROUND(H, c, d, a, b, in[0] + K3, 11);

  ROUND(H, b, c, d, a, in[4] + K3, 15);

  buf[0] += a;

  buf[1] += b;

  buf[2] += c;

  buf[3] += d;

}

#undef ROUND

#undef F

#undef G

#undef H

#undef K1

#undef K2

#undef K3

/* The old legacy hash */

static ext2_dirhash_t dx_hack_hash (const char *name, int len,

            int unsigned_flag)

{

  __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;

  const unsigned char *ucp = (const unsigned char *) name;

  const signed char *scp = (const signed char *) name;

  int c;

  while (len--) {

    if (unsigned_flag)

      c = (int) *ucp++;

    else

      c = (int) *scp++;

    hash = hash1 + (hash0 ^ (c * 7152373));

    if (hash & 0x80000000) hash -= 0x7fffffff;

    hash1 = hash0;

    hash0 = hash;

  }

  return (hash0 << 1);

}

static void str2hashbuf(const char *msg, int len, __u32 *buf, int num,

      int unsigned_flag)

{

  __u32 pad, val;

  int i, c;

  const unsigned char *ucp = (const unsigned char *) msg;

  const signed char *scp = (const signed char *) msg;

  pad = (__u32)len | ((__u32)len << 8);

  pad |= pad << 16;

  val = pad;

  if (len > num*4)

    len = num * 4;

  for (i=0; i < len; i++) {

    if (unsigned_flag)

      c = (int) ucp[i];

    else

      c = (int) scp[i];

    val = c + (val << 8);

    if ((i % 4) == 3) {

      *buf++ = val;

      val = pad;

      num--;

    }

  }

  if (--num >= 0)

    *buf++ = val;

  while (--num >= 0)

    *buf++ = pad;

}

/*

 * Returns the hash of a filename.  If len is 0 and name is NULL, then

 * this function can be used to test whether or not a hash version is

 * supported.

 *

 * The seed is an 4 longword (32 bits) "secret" which can be used to

 * uniquify a hash.  If the seed is all zero's, then some default seed

 * may be used.

 *

 * A particular hash version specifies whether or not the seed is

 * represented, and whether or not the returned hash is 32 bits or 64

 * bits.  32 bit hashes will return 0 for the minor hash.

 *

 * This function doesn't do any normalization or casefolding of the

 * input string.  To take charset encoding into account, use

 * ext2fs_dirhash2.

 *

 */

errcode_t ext2fs_dirhash(int version, const char *name, int len,

       const __u32 *seed,

       ext2_dirhash_t *ret_hash,

       ext2_dirhash_t *ret_minor_hash)

{

  __u32 hash;

  __u32 minor_hash = 0;

  const char  *p;

  int   i;

  __u32     in[8], buf[4];

  int   unsigned_flag = 0;

  /* Initialize the default seed for the hash checksum functions */

  buf[0] = 0x67452301;

  buf[1] = 0xefcdab89;

  buf[2] = 0x98badcfe;

  buf[3] = 0x10325476;

  /* Check to see if the seed is all zero's */

  if (seed) {

    for (i=0; i < 4; i++) {

      if (seed[i])

        break;

    }

    if (i < 4)

      memcpy(buf, seed, sizeof(buf));

  }

  switch (version) {

  case EXT2_HASH_LEGACY_UNSIGNED:

    unsigned_flag++;

    /* fallthrough */

  case EXT2_HASH_LEGACY:

    hash = dx_hack_hash(name, len, unsigned_flag);

    break;

  case EXT2_HASH_HALF_MD4_UNSIGNED:

    unsigned_flag++;

    /* fallthrough */

  case EXT2_HASH_HALF_MD4:

    p = name;

    while (len > 0) {

      str2hashbuf(p, len, in, 8, unsigned_flag);

      halfMD4Transform(buf, in);

      len -= 32;

      p += 32;

    }

    minor_hash = buf[2];

    hash = buf[1];

    break;

  case EXT2_HASH_TEA_UNSIGNED:

    unsigned_flag++;

    /* fallthrough */

  case EXT2_HASH_TEA:

    p = name;

    while (len > 0) {

      str2hashbuf(p, len, in, 4, unsigned_flag);

      TEA_transform(buf, in);

      len -= 16;

      p += 16;

    }

    hash = buf[0];

    minor_hash = buf[1];

    break;

  default:

    *ret_hash = 0;

    return EXT2_ET_DIRHASH_UNSUPP;

  }

  *ret_hash = hash & ~1;

  if (ret_minor_hash)

    *ret_minor_hash = minor_hash;

  return 0;

}

/*

 * Returns the hash of a filename considering normalization and

 * casefolding.  This is a wrapper around ext2fs_dirhash with string

 * encoding support based on the nls_table and the flags. Check

 * ext2fs_dirhash for documentation on the input and output parameters.

 */

errcode_t ext2fs_dirhash2(int version, const char *name, int len,

        const struct ext2fs_nls_table *charset,

        int hash_flags, const __u32 *seed,

        ext2_dirhash_t *ret_hash,

        ext2_dirhash_t *ret_minor_hash)

{

  errcode_t r;

  int dlen;

  if (len && charset && (hash_flags & EXT4_CASEFOLD_FL)) {

    char buff[PATH_MAX];

    dlen = charset->ops->casefold(charset,

            (const unsigned char *) name, len,

            (unsigned char *) buff, sizeof(buff));

    if (dlen < 0) {

      if (dlen == -EINVAL)

        goto opaque_seq;

      return dlen;

    }

    r = ext2fs_dirhash(version, buff, dlen, seed, ret_hash,

           ret_minor_hash);

    return r;

  }

opaque_seq:

  return ext2fs_dirhash(version, name, len, seed, ret_hash,

            ret_minor_hash);

}